A better recommendation would be 'don't ship JavaScript to oldIE'.
IE 6-8 have terrible JavaScript engines, JavaScript is going to do very little to help you deliver a good experience to users stuck on those browsers. For websites, let these users round-trip to the server for form-submissions, links etc. Progressively enhance with JS for IE9+
If you have commercial customers stuck on oldIE and have to deliver a single-page web app, your answer is Chrome Frame (and yes I've had experience asking customers on corporate networks to install Chrome Frame and had no objections/problems yet, as long as you're up-front with them).
IE 6-8 have terrible JavaScript engines, JavaScript is going to do very little to help you deliver a good experience to users stuck on those browsers. For websites, let these users round-trip to the server for form-submissions, links etc. Progressively enhance with JS for IE9+
If you have commercial customers stuck on oldIE and have to deliver a single-page web app, your answer is Chrome Frame (and yes I've had experience asking customers on corporate networks to install Chrome Frame and had no objections/problems yet, as long as you're up-front with them).